Rock Shell (also known as Castor Bean Rock Shell)
Phylum: Mollusca, Class: Gastropoda, Order: Neogastropoda, Family: Muricidae, Genus: Purpura, Species: Purpura persica · Muricidae (Murex family) · Gastropod, whole shell, spiral shape
Species
Purpura persica
Shell Type
Gastropod, whole shell, spiral shape
Family
Muricidae (Murex family)
Size
Approximately 1.5 to 2 inches, which is within the normal adult range for this species. Adults typically range from 1 to 3 inches.
Color & Pattern
A striking contrast of deep chocolate brown to nearly black markings splashed over a creamy white or light tan base, featuring vivid dark spiral bands and mottled patterns.
Rarity
Common
Habitat
Found on rocky intertidal shores, rocky reefs, and tide pools, clinging tightly to rocks in areas of heavy surf and wave action.
Geographic Range
Indo-West Pacific region, ranging from the East African coast across the Indian Ocean to Southeast Asia, Northern Australia, and Polynesia.
Description
A sturdy, heavy-bodied marine snail with a low spire, wide body whorl, and a heavily armored exterior covered in rows of blunt tubercles and knobs. The surface displays rich contrast patterns of dark brown and white.
Key Features
Low spire, heavily tuberculate or knobby exterior, wide aperture with a flattened columella, and strong ridges on the outer lip.
Collector Value
Moderately popular among shell collectors as a representative of the Muricidae family. Common specimens hold low to moderate value, typically ranging from a few dollars to under twenty dollars.
Condition Notes
The specimen is in good to fine condition, retaining strong natural coloration with minimal wear on the prominent knobs, indicating a well-preserved beach or shallow-water find.
Interesting Facts
Like many members of the Muricidae family, Purpura species can secrete a yellowish fluid that turns into a durable purple dye when exposed to sunlight, historically used to dye royal garments.
Ecological Role
Carnivorous predator that feeds on barnacles, bivalves, and other intertidal invertebrates, helping to control prey populations in rocky shore ecosystems.
Similar Species
Purpura panama or other Purpura and Thais species, which can be distinguished by differences in nodule arrangement and aperture coloration.
Beach Finding Tips
Search along rocky shorelines and tide pools during extreme low tide, specifically looking under rock ledges or in crevices where they shelter from heavy surf.